1. Field of the Invention
The present invention relates to a staging apparatus having an anti-vibration mechanism which is suitable for use with a stage for positioning a photosensitive substrate in a projection exposure apparatus or a stage for moving an object while it carries the object in a measurement instrument.
2. Related Background Art
When a semiconductor device or a liquid crystal display device is to be manufactured in a photo-lithography process, a projection exposure apparatus which exposes a pattern image of a photomask or a reticle onto a photosensitive substrate by a step and repeat process through a projection optical system is used. In such a projection exposure apparatus, since it is required to precisely position the photo-sensitive substrate, a stage which mounts the photo-sensitive substrate and moves it three-dimensionally is used.
In the prior art projection exposure apparatus, in order to prevent an external disturbance from the external of the apparatus and an internal vibration generated in the apparatus from deteriorating performances of the projection exposure apparatus, the entire projection exposure apparatus is mounted on a vibration attenuation apparatus called an anti-vibration table. However, as the size of the photo-sensitive substrate increases, the weight of a moving portion of the stage increases, and as the speed of the stage increases, a counterforce applied to the anti-vibration table (the entire apparatus) from the stage increases more and more. As the counterforce increases more and more, a vibration amplitude generated in the anti-vibration table increases, and the vibration acts to the stage to lead to the deterioration of a settling time of the positioning of the stage (a time required for a positional deviation of the stage from a target position to reach substantially zero) and a stop precision.
In order to improve the settling time of the positioning of the stage and the stop precision, an active anti-vibration mechanism which detects the generated vibration by a gradient sensor or an acceleration sensor and actively controls the detected vibration by an actuator may be used. By the use of such an anti-vibration mechanism, the reduction of the vibration settling time in the anti-vibration table may be expected and the improvement of the stage performance may be expected.
However, even when the active anti-vibration mechanism is adopted, the anti-vibration is still based on a principle that the generated vibration is converted to an electrical signal by a sensor and the detected signal is fed back to the actuator. Accordingly, a response time before the suppression of the generated vibration is not short enough and the tracking property of the anti-vibration operation to the generated vibration is poor.